One conventionally widely used method for forming, for example, inner electrodes of laminated condensers, conductive patterns of circuit boards, and electrodes and circuits of substrates for solar cells and plasma display panels is a method including: adding a silver powder to an organic vehicle together with a glass frit, followed by kneading, to thereby produce a conductive paste of a burning type; forming the produced conductive paste on a substrate in a predetermined pattern; and heating the resultant at a temperature of 500° C. or higher to remove organic components and sinter the silver powder particles together, to thereby form a conductive film.
Conductive pastes used for such applications are required to respond to, for example, higher densification and finer lines of conductive patterns in order to achieve downsizing of electronic parts. Therefore, silver powders used are required, for example, to have appropriately small particle diameters and uniform particle sizes and to be dispersed in an organic vehicle.
A known method for producing a silver powder for such a conductive paste is a wet reduction method of adding a reducing agent to an aqueous reaction system containing silver ions to deposit spherical silver powder through reduction (see, for example, PTL 1).
Another known method is a method of substituting an organic substance imparted onto the surface of nano-size silver powder with an appropriate one, to thereby improve compatibility with a predetermined organic vehicle (see, for example, PTL 2).